The development of chemical nomenclature for polymeric substances is an ongoing endeavour. Over recent decades, some of the general principles and details on how to name polymers have changed. The first IUPAC document on structure-based nomenclature of single-strand polymers  named, for example, the polymer obtained from tetrahydrofuran (oxolane) through cationic polymerization, poly(oxytetramethylene). At that time, polypropylene was a systematic name, the constitutional unit –CH2–CH2– was named ethylene, and the –CH=CH–CH2–CH2– unit was named 1-butenylene, to give only few examples of then up-to-date nomenclature. As organic-chemical nomenclature developed, a necessary revision of  appeared, published in 2002 . The “polymethylene” names (e.g., hexamethylene), as well as the alkylene names for constitutional units (e.g., butylene) were abandoned in favour of alkane-1,x-diyl, and further changes were made to accord with organic-chemical nomenclature , . Minor revisions of  were also made in the 2nd edition of the Compendium of Polymer Terminology and Nomenclature, “The Purple Book” . Changes in recently issued new editions of the IUPAC Nomenclature of Organic Chemistry (“The Blue Book”)  and Nomenclature of Inorganic Chemistry (“The Red Book”)  again have implications for naming polymers.
There are two principal approaches to naming polymers , source-based nomenclature and structure-based nomenclature. Source-based nomenclature uses the IUPAC names of the monomer or monomers from which the polymer is presumed to have been prepared. Structure-based nomenclature uses IUPAC nomenclature for the constitutional units of the constituent macromolecules. In this document, constitutional units are collated only for structure-based names; for source-based names of polymers, the names of units, the monomer units, to be used are those recommended in the IUPAC nomenclature of organic  and inorganic  chemistry and in the new document on source-based nomenclature .
Published rules ,  give clear instructions on how to determine constitutional repeating units (CRUs) and the order of their subunits in a regular macromolecule. These rules lead to a single, preferred CRU, i.e., a unique structure (sequence of constitutional units), which is the basis for naming a polymer by structure-based nomenclature. However, for many constitutional units (CUs) there is more than one possibility of naming them, which results in a number of different possible structure-based names for a given polymer. These different possibilities have been favoured differently at different times, and have been sources of inconsistencies.
One principal rule in polymer nomenclature is that the names of constitutional units and monomer units must be those recommended in organic-chemical nomenclature. Therefore, in structure-based polymer nomenclature the names of the corresponding groups in organic chemistry should be used for each CU. Because of this, there seems to be no need to discuss the naming of CUs or CRUs. However, polymer nomenclature has some specific requirements, which in a number of cases will lead to a different name. One of these requirements is expressed in the very basic rule used in structure-based polymer nomenclature: groups not constituting the backbone of a macromolecule are always named as substituents. This rule overrides the above-mentioned principal rule, which results in the situation that in practice a large number of CRUs will have names that differ from the names these groups have in organic-chemical nomenclature.
One example is the group –CH(CH3)–CH2–, called propane-1,2-diyl in organic chemistry. This name is not used in polymer nomenclature, because, at least with the order of locants (-1,2-), it would refer to a different orientation of the constitutional unit. If one follows the selection rules for the determination of the preferred CRU, the name would have to be propane-2,1-diyl. More importantly, however, the general rule for naming groups that do not constitute the backbone (here the methyl group) as substituents leaves a substituted –CH2–CH2– group in the backbone. This results in the name 1-methylethylene for this example, or more systematically, 1-methylethane-1,2-diyl. As with this example, a number of preferred names in the context of organic-chemical nomenclature will therefore have to be stated as being incorrect in contexts within polymer nomenclature. However, for each part of the constitutional unit (structure) the corresponding component name should still be that used in organic-chemical nomenclature. These principles also apply to the naming of inorganic or hybrid organic-inorganic polymers.
Another example is the group –CH2–CH2–, a very important CU in the naming of polymers, being probably the most frequently occurring CU in polymer nomenclature. There are two names for this constitutional unit:
the traditional name ethylene, and
the systematic name ethane-1,2-diyl.
The former is in common usage, while in  the latter is recommended for use in a preferred IUPAC name (PIN), the argument being that this name is more systematic.
Replacement of the name ethylene with ethane-1,2-diyl, as done in the Purple Book , would result in new and longer names for a large number of polymers (in particular polymers of industrial importance) without gaining any advantage. Therefore, it is recommended that the preferred name for the group –CH2–CH2– in structure-based polymer nomenclature remains ethylene. The unfortunate change of the respective names in the Purple Book  was based on the erroneous assumption that the Blue Book  would abandon the name ethylene completely.
Recommendations in this document attempt to remove inconsistencies in structure-based polymer nomenclature and aim to make a clear statement as to which of the diverse names of CUs are still recommended and which of several alternative acceptable names is the preferred one. The document is restricted to single-strand polymers, because the vast majority of polymers has this structural feature.
This document consists mainly of two tables, together with explanatory footnotes and a section on how to use the tables. As the whole document will be searchable, the authors hope that anyone having to deal with polymer nomenclature will use this collection of constitutional units for correctly naming polymers.
The preferred names of constitutional units in Table 1 should be used in structure-based names of regular and irregular polymers (e.g., constitutional repeating units, subunits of constitutional repeating units, junction units, and single constitutional units in names of irregular polymers).
PNP-1 Principles of structure-based nomenclature for polymers
The principles of structure-based polymer nomenclature have been described in detail in Refs. , , ,  for regular and irregular polymers. Concise versions are given in Refs. , , . Depending on how detailed the available knowledge of the structure is, the structure-based name of a polymer is long and the application of the rules of organic-chemical nomenclature in the frame of polymer nomenclature can be tedious. Examples can be found in the IUPAC recommendations on cyclic organic macromolecules .
Regular polymers consist of macromolecules, the structure of which essentially comprises the repetition of a single constitutional unit, with all units connected identically with respect to directional sense (definition from Ref. , p. 4). In the vast majority of cases, regular polymers have idealized structures where irregularities are neglected.
A constitutional unit (CU) is an atom or a group of atoms (with pendant atoms or groups, if any) comprising a part of the essential structure of a macromolecule, an oligomer molecule, a regular block, or a regular chain (definition from Ref. , p. 5).
A constitutional repeating unit (CRU) is the smallest constitutional unit, the repetition of which constitutes a regular macromolecule, a regular oligomer molecule, a regular block, or a regular chain (definition from Ref. , p. 5).
Structure-based nomenclature of regular polymers uses the name of the preferred CRU. It is determined as follows:
a part of the polymer chain large enough to show the structural repetition is drawn, typically,
the smallest repeating portion is a CRU where all possibilities in either direction are identified, in this case:
the next step is to identify the subunits that make up each of these structures, i.e., the largest groups that can be named using IUPAC nomenclature of organic or (when appropriate) inorganic chemistry,
the correct order of the subunits, that of decreasing seniority is then determined, and if this leaves a choice
the preferred CRU is that with the lowest possible locant(s) for substituents.
Commonly, the preferred CRU of a polymer is written citing its subunits in decreasing order of seniority from left to right, i.e., for the above example:
Using the CU names of entries 152 and 29 in Table 1, the name of this polymer will be: poly[oxy(1-bromoethylene)].
However, it should be noted that the correct name for the preferred CRU is independent of how the formula is actually drawn. For example:
Both structural representations are correct, and the correct name for both is poly[azanediyl(1-oxohexane-1,6-diyl)], applying the above-mentioned rules for the determination of the CRU with entries 159 and 93 from Table 1.
Irregular polymers consist of macromolecules where the structure essentially comprises the repetition of more than one type of constitutional unit or of macromolecules whose structure comprises constitutional units not all identically connected with respect to directional sense (definition from Ref. , p. 4).
Irregular polymers are named by placing the prefix “poly” before the structure-based names of the constitutional units, collectively enclosed in parentheses or brackets, with the individual constitutional units separated by oblique strokes.
A simple example of an irregular polymer is the polymer derived from chloroethene, the units of which are linked both head-to-tail and head-to-head:
The constitutional units are:
The name of the polymer is: poly[(1-chloroethylene)/(2-chloroethylene)] with entries 32 and 33 from Table 1.
For details on structure-based nomenclature of irregular polymers see Ref. .
PNP-2 Constitutional units for naming polymers
Constitutional units (CUs) for naming common polymers (commercial or otherwise well-known) and CUs that have been used in IUPAC documents on polymer nomenclature and terminology have been identified and collected in Table 1. This table includes the chemical formula of each CU and its preferred name, which should be used when naming a polymer. The column headed, “Other acceptable names of CU” contains acceptable alternative names. The next column lists names for these CUs which should no longer be used because they are outdated, ambiguous, or incorrect for various reasons, typically:
a change of recommendations concerning the position of locants in a name, e.g., “but-1-ene-1,4-diyl” not “1-butene-1,4-diyl”;
the use of a substituted “ethylene” instead of alkane-1,2-diyl, e.g., “1-methylethylene” not “propane-1,2-diyl”;
former use for different structures, e.g., propylene.
Formulae in Table 1 are drawn with “open” bonds for free valences, as is common in polymer chemistry, when the element symbols of the atoms with the free valences are shown. A wavy (wiggly) line perpendicular to the end of each bond line, indicating a free valence of a CU, is used in accordance with  if any element symbol of an atom with a free valence in this CU is not shown.
Names of CUs which are always enclosed in enclosing marks (substituted subunits) are shown with the corresponding enclosing marks in the table. CUs without enclosing marks in Table 1 are not parenthesised in a polymer name, except when they constitute the only and complete CRU.
In Table 1, these names have been arranged to facilitate location of a constitutional unit for the convenience of the reader. Entries are arranged in 6 groups:
carbon chains according to number of chain atoms and degree of unsaturation;
carbon rings according to ring size and degree of unsaturation;
chains containing hetero atoms;
heterocycles according to ring size and number and type of hetero atoms;
units with connectivity greater than two.
Entries within these groups are listed in order of increasing complexity (unsubstituted, mono- and multiply- substituted, number and size of rings). Structural formulae in most cases are written in decreasing order of seniority of subunits as they will appear in a preferred CRU (see PNP-1) when reading from left to right. In some cases (e.g., blocks linked to each other in a particular way, single [linking] constitutional units, or irregular polymers) a different order or orientation of constitutional units will result, and the name of the corresponding CU in the polymer name will reflect this. Some names that deviate from a name for a preferred CRU (if the polymer is composed of this CU only) are exemplified in entries 33 and 76 in Table 1.
Reasons as to why some names of CUs are no longer acceptable are given in the corresponding column or explained in footnotes, which can be found at the end of the table (p. ##).
In Tables 1 and 2 (but not in the rest of this document!), the symbol = is used to split names too long for the column format, unless there is a convenient hyphen already present in the name. This symbol indicates that a) the name continues on the next line, b) this symbol is removed when the name is not broken at this position at the end of a line, and c) there is no space in this position of the name. Note that in normal typesetting a normal hyphen, -, is used in such situations. The symbol = is only used for clarity in the tables of this document.
PNP-3 Structure-based, source-based and traditional names of common polymers
A number of common polymers have source-based names and semi-systematic or trivial names in addition to structure-based names. These additional names are well established by usage because they are also used for regulatory purposes. Changing to a correct structure- or source-based name would require changes in many official and regulatory documents. The most important of these names are included in the following Table 2. In general, however, the use of semi-systematic or trivial names for polymers should be kept to a minimum. In particular, ambiguous names or names not based on any systematic type of nomenclature should not be used at all.
Table 2 contains idealized structural representations, the corresponding structure-based names, and source-based names. Equivalent names for close analogues of these polymers [e.g., other alkyl ester analogues of poly(methyl acrylate) or ester analogues of poly(vinyl acetate)] are also acceptable, as long as the alkyl and acid names, respectively, are retained names . Further, Table 2 contains a limiting list of retained traditional polymer names.
The terminology used in this context is mainly derived from usage in the so-called IUPAC “Blue Book”, “Nomenclature of Organic Chemistry” . The relevant terms and their meanings are given here:
Preferred IUPAC name (PIN)
A name preferred among two or more names generated from two or more IUPAC recommendations, including the many synonyms that have been coined and used over the years.
General IUPAC nomenclature
The principles, rules, and conventions by which IUPAC names other than preferred IUPAC names (PINs) are generated.
A traditional name, a name in common use retained either as the preferred IUPAC name or as an alternative name in general IUPAC nomenclature (e.g., benzoic acid or polyethylene).
In addition, the following term is important in the context of classifying polymer names.
A name in common use within one or more sectors of the chemical community.
A number of existing IUPAC recommendations on polymer nomenclature and terminology has been screened in terms of naming and the names of polymers. From these, a list of constitutional units (CU) used for naming polymers according to IUPAC nomenclature rules has been made (PNP-2). This list also comprises CUs of commercial and well-known polymers. A preferred name is provided for each CU. Other acceptable names and names which are not acceptable because they are outdated or ambiguous or incorrect, although they may have been correct in the past or in a different context, are also listed. In a second table (PNP-3), names of common polymers are given. This table includes structure-based names, source-based names, retained traditional polymer names, and not acceptable names. These tables replace similar tables in previous documents. The preferred names of constitutional units in Table 1 should be used in structure-based names of regular and irregular polymers. It is hoped that the entries in this document’s tables can be searched using the functions provided by web browsers, or by programs for reading pdf-files; this should facilitate the construction of names using the names for CUs and common polymers given in the tables.
Membership of sponsoring bodies
Membership of the Division Committee of the IUPAC Division of Chemical Nomenclature and Structure Representation for the period 2016–2017 was as follows:
President: K.-H. Hellwich (Germany); Vice President: A. T. Hutton (South Africa); Secretary: R. S. Laitinen (Finland); Titular Members: O. Achmatowicz (Poland); T. Damhus (Denmark); P. Hodge (UK); R. Macaluso (USA); J. Nagy (Hungary); M. M. Rogers (USA); J. Vohlídal (Czech Republic); Associate Members: M. A. Beckett (UK); I. L. Dukov (Bulgaria); G. A. Eller (Austria); E. Mansfield (USA); M. A. Strausbaugh (USA); K. T. Taylor (USA); National Representatives: F. Aricò (Italy); A. M. da Costa Ferreira (Brazil); A. Fradet (France); H. W. Lee (Korea); T. L. Lowary (Canada); E. Nordlander (Sweden); M. Putala (Slovakia); A. P. Rauter (Portugal); J. P. van Lune (Netherlands); A. Yerin (Russia); Ex Officio: R. M. Hartshorn (New Zealand); G. P. Moss (UK).
Membership of the IUPAC Polymer Division Committee for the period 2016–2017 was as follows:
President: G. T. Russell (New Zealand); Vice President: C. K. Luscombe (USA); Secretary: M. G. Walter (USA); Past President: M. Buback (Germany); Titular Members: S. Beuermann (Germany); J. He (China); I. Lacík (Slovakia); M. Sawamoto (Japan); N. Stingelin (UK); Y. Yagci (Turkey); Associate Members: R. C. Hiorns (France); M. Hess (Germany); R. Hutchinson (Canada); G. Moad (Australia); R. Advincula (USA); D. Auhl (Netherlands); National Representatives: R. Adhikari (Nepal); M. C. H. Chan (Malaysia); C. dos Santos (Brazil); V. P. Hoven (Thailand); C.-S. Hsu (Taiwan); R. G. Jones (UK); D. S. Lee (Korea); M. Malinconico (Italy); O. Philippova (Russia); J. Vohlídal (Czech Republic).
Membership of the Subcommittee on Polymer Terminology during the preparation of this document (2008–2016) was as follows: Chair: R. G. Jones (UK), 2006–2013; R. C. Hiorns (France), from 2014; Secretary: T. Kitayama (Japan), 2008–2009; R. C. Hiorns (France), 2010–2013; C. K. Luscombe (USA), 2014–2015; P. D. Topham (UK), from 2016; Members: R. Adhikari (Nepal); G. Allegra (Italy); M. Barón (Argentina); R. Boucher (UK); T. Chang (Korea); J. Chen (USA); C. Fellows (Australia); A. Fradet (France); K. Hatada (Japan); J. He (China); K.H. Hellwich (Germany); M. Hess (Germany); R. C. Hiorns (France); P. Hodge (UK); K. Horie1 (Japan); A. D. Jenkins (UK); J.I. Jin (Korea); R. G. Jones (UK); J. Kahovec (Czech Republic); T. Kitayama (Japan); P. Kratochvíl (Czech Republic); P. Kubisa (Poland); C. K. Luscombe (USA); E. Maréchal1 (France); S. V. Meille (Italy); I. Meisel (Germany); W. V. Metanomski1 (USA); I. Mita1 (Japan); G. Moad (Australia); W. Mormann (Germany); N. Nakabayashi (Japan); T. Nakano (Japan); C. K. Ober (USA); S. Penczek (Poland); M. D. Purbrick (UK); L. P. Rebelo (Portugal); M. Rinaudo (France); G. Russell (New Zealand); C. dos Santos (Brazil); I. Schopov (Bulgaria); C. Scholz (USA); F. Schué1 (France); V. P. Shibaev (Russia); S. Słomkowski (Poland); D. W. Smith (USA); R. F. T. Stepto1 (UK); N. Stingelin (UK); D. Tabak (Brazil); P. D. Topham (UK); J.-P. Vairon (France); M. Vert (France); J. Vohlídal (Czech Republic); M. G. Walter (USA); E. S. Wilks (USA); W. J. Work (USA).
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About the article
Published Online: 2017-09-26
Published in Print: 2017-10-26
Funding: International Union of Pure and Applied Chemistry, (Grant/Award Number: ‘2008-015-1-400’).
Citation Information: Pure and Applied Chemistry, Volume 89, Issue 11, Pages 1695–1736, ISSN (Online) 1365-3075, ISSN (Print) 0033-4545, DOI: https://doi.org/10.1515/pac-2016-0502.http://creativecommons.org/licenses/by-nc-nd/4.0/.